A known crash box is placed between a bumper reinforcement provided in a front portion of a vehicle and a hollow side member (side frame) provided on a side of the vehicle and is configured to be deformed in the event of a collision of the vehicle, so as to absorb the collision energy (as described in, for example, Patent Literature 1). A crash box described in Patent Literature 1 has a tubular body that is formed by deep drawing of a steel plate and that has a bottomed leading end and a flange formed around an outer periphery of an opening end. A bottom of the leading end is fixed to the bumper reinforcement, and the flange is fixed to a mounting portion that is provided in the outer periphery of the opening end of the side member. A part from the opening end of the tubular body to the flange is formed as an inverting part that is curled in a trough shape toward the bumper reinforcement side. This crash box has a turning deformation that causes the tubular body to enter the side member from the inverting part as the starting point, in the event of a collision of the vehicle, so as to absorb the collision energy.